Chapter 14 – Deep Computer Vision Using Convolutional Neural Networks
This notebook contains all the sample code in chapter 14.
First, let's import a few common modules, ensure MatplotLib plots figures inline and prepare a function to save the figures. We also check that Python 3.5 or later is installed (although Python 2.x may work, it is deprecated so we strongly recommend you use Python 3 instead), as well as Scikit-Learn ≥0.20 and TensorFlow ≥2.0.
# Python ≥3.5 is required
import sys
assert sys.version_info >= (3, 5)
# Is this notebook running on Colab or Kaggle?
IS_COLAB = "google.colab" in sys.modules
IS_KAGGLE = "kaggle_secrets" in sys.modules
# Scikit-Learn ≥0.20 is required
import sklearn
assert sklearn.__version__ >= "0.20"
# TensorFlow ≥2.0 is required
import tensorflow as tf
from tensorflow import keras
assert tf.__version__ >= "2.0"
if not tf.config.list_physical_devices('GPU'):
print("No GPU was detected. CNNs can be very slow without a GPU.")
if IS_COLAB:
print("Go to Runtime > Change runtime and select a GPU hardware accelerator.")
if IS_KAGGLE:
print("Go to Settings > Accelerator and select GPU.")
# Common imports
import numpy as np
import os
# to make this notebook's output stable across runs
np.random.seed(42)
tf.random.set_seed(42)
# To plot pretty figures
%matplotlib inline
import matplotlib as mpl
import matplotlib.pyplot as plt
mpl.rc('axes', labelsize=14)
mpl.rc('xtick', labelsize=12)
mpl.rc('ytick', labelsize=12)
# Where to save the figures
PROJECT_ROOT_DIR = "."
CHAPTER_ID = "cnn"
IMAGES_PATH = os.path.join(PROJECT_ROOT_DIR, "images", CHAPTER_ID)
os.makedirs(IMAGES_PATH, exist_ok=True)
def save_fig(fig_id, tight_layout=True, fig_extension="png", resolution=300):
path = os.path.join(IMAGES_PATH, fig_id + "." + fig_extension)
print("Saving figure", fig_id)
if tight_layout:
plt.tight_layout()
plt.savefig(path, format=fig_extension, dpi=resolution)
A couple utility functions to plot grayscale and RGB images:
def plot_image(image):
plt.imshow(image, cmap="gray", interpolation="nearest")
plt.axis("off")
def plot_color_image(image):
plt.imshow(image, interpolation="nearest")
plt.axis("off")
import numpy as np
from sklearn.datasets import load_sample_image
# Load sample images
china = load_sample_image("china.jpg") / 255
flower = load_sample_image("flower.jpg") / 255
images = np.array([china, flower])
batch_size, height, width, channels = images.shape
# Create 2 filters
filters = np.zeros(shape=(7, 7, channels, 2), dtype=np.float32)
filters[:, 3, :, 0] = 1 # vertical line
filters[3, :, :, 1] = 1 # horizontal line
outputs = tf.nn.conv2d(images, filters, strides=1, padding="SAME")
plt.imshow(outputs[0, :, :, 1], cmap="gray") # plot 1st image's 2nd feature map
plt.axis("off") # Not shown in the book
plt.show()
for image_index in (0, 1):
for feature_map_index in (0, 1):
plt.subplot(2, 2, image_index * 2 + feature_map_index + 1)
plot_image(outputs[image_index, :, :, feature_map_index])
plt.show()
def crop(images):
return images[150:220, 130:250]
plot_image(crop(images[0, :, :, 0]))
save_fig("china_original", tight_layout=False)
plt.show()
for feature_map_index, filename in enumerate(["china_vertical", "china_horizontal"]):
plot_image(crop(outputs[0, :, :, feature_map_index]))
save_fig(filename, tight_layout=False)
plt.show()
plot_image(filters[:, :, 0, 0])
plt.show()
plot_image(filters[:, :, 0, 1])
plt.show()
Let's create a 2D convolutional layer, using keras.layers.Conv2D():
np.random.seed(42)
tf.random.set_seed(42)
conv = keras.layers.Conv2D(filters=2, kernel_size=7, strides=1,
padding="SAME", activation="relu", input_shape=outputs.shape)
Let's call this layer, passing it the two test images:
conv_outputs = conv(images)
conv_outputs.shape
The output is a 4D tensor. The dimensions are: batch size, height, width, channels. The first dimension (batch size) is 2 since there are 2 input images. The next two dimensions are the height and width of the output feature maps: since padding="SAME" and strides=1, the output feature maps have the same height and width as the input images (in this case, 427×640). Lastly, this convolutional layer has 2 filters, so the last dimension is 2: there are 2 output feature maps per input image.
Since the filters are initialized randomly, they'll initially detect random patterns. Let's take a look at the 2 output features maps for each image:
plt.figure(figsize=(10,6))
for image_index in (0, 1):
for feature_map_index in (0, 1):
plt.subplot(2, 2, image_index * 2 + feature_map_index + 1)
plot_image(crop(conv_outputs[image_index, :, :, feature_map_index]))
plt.show()
Although the filters were initialized randomly, the second filter happens to act like an edge detector. Randomly initialized filters often act this way, which is quite fortunate since detecting edges is quite useful in image processing.
If we want, we can set the filters to be the ones we manually defined earlier, and set the biases to zeros (in real life we will almost never need to set filters or biases manually, as the convolutional layer will just learn the appropriate filters and biases during training):
conv.set_weights([filters, np.zeros(2)])
Now let's call this layer again on the same two images, and let's check that the output feature maps do highlight vertical lines and horizontal lines, respectively (as earlier):
conv_outputs = conv(images)
conv_outputs.shape
plt.figure(figsize=(10,6))
for image_index in (0, 1):
for feature_map_index in (0, 1):
plt.subplot(2, 2, image_index * 2 + feature_map_index + 1)
plot_image(crop(conv_outputs[image_index, :, :, feature_map_index]))
plt.show()
def feature_map_size(input_size, kernel_size, strides=1, padding="SAME"):
if padding == "SAME":
return (input_size - 1) // strides + 1
else:
return (input_size - kernel_size) // strides + 1
def pad_before_and_padded_size(input_size, kernel_size, strides=1):
fmap_size = feature_map_size(input_size, kernel_size, strides)
padded_size = max((fmap_size - 1) * strides + kernel_size, input_size)
pad_before = (padded_size - input_size) // 2
return pad_before, padded_size
def manual_same_padding(images, kernel_size, strides=1):
if kernel_size == 1:
return images.astype(np.float32)
batch_size, height, width, channels = images.shape
top_pad, padded_height = pad_before_and_padded_size(height, kernel_size, strides)
left_pad, padded_width = pad_before_and_padded_size(width, kernel_size, strides)
padded_shape = [batch_size, padded_height, padded_width, channels]
padded_images = np.zeros(padded_shape, dtype=np.float32)
padded_images[:, top_pad:height+top_pad, left_pad:width+left_pad, :] = images
return padded_images
Using "SAME" padding is equivalent to padding manually using manual_same_padding() then using "VALID" padding (confusingly, "VALID" padding means no padding at all):
kernel_size = 7
strides = 2
conv_valid = keras.layers.Conv2D(filters=1, kernel_size=kernel_size, strides=strides, padding="VALID")
conv_same = keras.layers.Conv2D(filters=1, kernel_size=kernel_size, strides=strides, padding="SAME")
valid_output = conv_valid(manual_same_padding(images, kernel_size, strides))
# Need to call build() so conv_same's weights get created
conv_same.build(tf.TensorShape(images.shape))
# Copy the weights from conv_valid to conv_same
conv_same.set_weights(conv_valid.get_weights())
same_output = conv_same(images.astype(np.float32))
assert np.allclose(valid_output.numpy(), same_output.numpy())
max_pool = keras.layers.MaxPool2D(pool_size=2)
cropped_images = np.array([crop(image) for image in images], dtype=np.float32)
output = max_pool(cropped_images)
fig = plt.figure(figsize=(12, 8))
gs = mpl.gridspec.GridSpec(nrows=1, ncols=2, width_ratios=[2, 1])
ax1 = fig.add_subplot(gs[0, 0])
ax1.set_title("Input", fontsize=14)
ax1.imshow(cropped_images[0]) # plot the 1st image
ax1.axis("off")
ax2 = fig.add_subplot(gs[0, 1])
ax2.set_title("Output", fontsize=14)
ax2.imshow(output[0]) # plot the output for the 1st image
ax2.axis("off")
save_fig("china_max_pooling")
plt.show()
class DepthMaxPool(keras.layers.Layer):
def __init__(self, pool_size, strides=None, padding="VALID", **kwargs):
super().__init__(**kwargs)
if strides is None:
strides = pool_size
self.pool_size = pool_size
self.strides = strides
self.padding = padding
def call(self, inputs):
return tf.nn.max_pool(inputs,
ksize=(1, 1, 1, self.pool_size),
strides=(1, 1, 1, self.pool_size),
padding=self.padding)
depth_pool = DepthMaxPool(3)
with tf.device("/cpu:0"): # there is no GPU-kernel yet
depth_output = depth_pool(cropped_images)
depth_output.shape
Or just use a Lambda layer:
depth_pool = keras.layers.Lambda(lambda X: tf.nn.max_pool(
X, ksize=(1, 1, 1, 3), strides=(1, 1, 1, 3), padding="VALID"))
with tf.device("/cpu:0"): # there is no GPU-kernel yet
depth_output = depth_pool(cropped_images)
depth_output.shape
plt.figure(figsize=(12, 8))
plt.subplot(1, 2, 1)
plt.title("Input", fontsize=14)
plot_color_image(cropped_images[0]) # plot the 1st image
plt.subplot(1, 2, 2)
plt.title("Output", fontsize=14)
plot_image(depth_output[0, ..., 0]) # plot the output for the 1st image
plt.axis("off")
plt.show()
avg_pool = keras.layers.AvgPool2D(pool_size=2)
output_avg = avg_pool(cropped_images)
fig = plt.figure(figsize=(12, 8))
gs = mpl.gridspec.GridSpec(nrows=1, ncols=2, width_ratios=[2, 1])
ax1 = fig.add_subplot(gs[0, 0])
ax1.set_title("Input", fontsize=14)
ax1.imshow(cropped_images[0]) # plot the 1st image
ax1.axis("off")
ax2 = fig.add_subplot(gs[0, 1])
ax2.set_title("Output", fontsize=14)
ax2.imshow(output_avg[0]) # plot the output for the 1st image
ax2.axis("off")
plt.show()
global_avg_pool = keras.layers.GlobalAvgPool2D()
global_avg_pool(cropped_images)
output_global_avg2 = keras.layers.Lambda(lambda X: tf.reduce_mean(X, axis=[1, 2]))
output_global_avg2(cropped_images)
(X_train_full, y_train_full), (X_test, y_test) = keras.datasets.fashion_mnist.load_data()
X_train, X_valid = X_train_full[:-5000], X_train_full[-5000:]
y_train, y_valid = y_train_full[:-5000], y_train_full[-5000:]
X_mean = X_train.mean(axis=0, keepdims=True)
X_std = X_train.std(axis=0, keepdims=True) + 1e-7
X_train = (X_train - X_mean) / X_std
X_valid = (X_valid - X_mean) / X_std
X_test = (X_test - X_mean) / X_std
X_train = X_train[..., np.newaxis]
X_valid = X_valid[..., np.newaxis]
X_test = X_test[..., np.newaxis]
from functools import partial
DefaultConv2D = partial(keras.layers.Conv2D,
kernel_size=3, activation='relu', padding="SAME")
model = keras.models.Sequential([
DefaultConv2D(filters=64, kernel_size=7, input_shape=[28, 28, 1]),
keras.layers.MaxPooling2D(pool_size=2),
DefaultConv2D(filters=128),
DefaultConv2D(filters=128),
keras.layers.MaxPooling2D(pool_size=2),
DefaultConv2D(filters=256),
DefaultConv2D(filters=256),
keras.layers.MaxPooling2D(pool_size=2),
keras.layers.Flatten(),
keras.layers.Dense(units=128, activation='relu'),
keras.layers.Dropout(0.5),
keras.layers.Dense(units=64, activation='relu'),
keras.layers.Dropout(0.5),
keras.layers.Dense(units=10, activation='softmax'),
])
model.compile(loss="sparse_categorical_crossentropy", optimizer="nadam", metrics=["accuracy"])
history = model.fit(X_train, y_train, epochs=10, validation_data=(X_valid, y_valid))
score = model.evaluate(X_test, y_test)
X_new = X_test[:10] # pretend we have new images
y_pred = model.predict(X_new)
DefaultConv2D = partial(keras.layers.Conv2D, kernel_size=3, strides=1,
padding="SAME", use_bias=False)
class ResidualUnit(keras.layers.Layer):
def __init__(self, filters, strides=1, activation="relu", **kwargs):
super().__init__(**kwargs)
self.activation = keras.activations.get(activation)
self.main_layers = [
DefaultConv2D(filters, strides=strides),
keras.layers.BatchNormalization(),
self.activation,
DefaultConv2D(filters),
keras.layers.BatchNormalization()]
self.skip_layers = []
if strides > 1:
self.skip_layers = [
DefaultConv2D(filters, kernel_size=1, strides=strides),
keras.layers.BatchNormalization()]
def call(self, inputs):
Z = inputs
for layer in self.main_layers:
Z = layer(Z)
skip_Z = inputs
for layer in self.skip_layers:
skip_Z = layer(skip_Z)
return self.activation(Z + skip_Z)
model = keras.models.Sequential()
model.add(DefaultConv2D(64, kernel_size=7, strides=2,
input_shape=[224, 224, 3]))
model.add(keras.layers.BatchNormalization())
model.add(keras.layers.Activation("relu"))
model.add(keras.layers.MaxPool2D(pool_size=3, strides=2, padding="SAME"))
prev_filters = 64
for filters in [64] * 3 + [128] * 4 + [256] * 6 + [512] * 3:
strides = 1 if filters == prev_filters else 2
model.add(ResidualUnit(filters, strides=strides))
prev_filters = filters
model.add(keras.layers.GlobalAvgPool2D())
model.add(keras.layers.Flatten())
model.add(keras.layers.Dense(10, activation="softmax"))
model.summary()
model = keras.applications.resnet50.ResNet50(weights="imagenet")
images_resized = tf.image.resize(images, [224, 224])
plot_color_image(images_resized[0])
plt.show()
images_resized = tf.image.resize_with_pad(images, 224, 224, antialias=True)
plot_color_image(images_resized[0])
images_resized = tf.image.resize_with_crop_or_pad(images, 224, 224)
plot_color_image(images_resized[0])
plt.show()
china_box = [0, 0.03, 1, 0.68]
flower_box = [0.19, 0.26, 0.86, 0.7]
images_resized = tf.image.crop_and_resize(images, [china_box, flower_box], [0, 1], [224, 224])
plot_color_image(images_resized[0])
plt.show()
plot_color_image(images_resized[1])
plt.show()
inputs = keras.applications.resnet50.preprocess_input(images_resized * 255)
Y_proba = model.predict(inputs)
Y_proba.shape
top_K = keras.applications.resnet50.decode_predictions(Y_proba, top=3)
for image_index in range(len(images)):
print("Image #{}".format(image_index))
for class_id, name, y_proba in top_K[image_index]:
print(" {} - {:12s} {:.2f}%".format(class_id, name, y_proba * 100))
print()
import tensorflow_datasets as tfds
dataset, info = tfds.load("tf_flowers", as_supervised=True, with_info=True)
info.splits
info.splits["train"]
class_names = info.features["label"].names
class_names
n_classes = info.features["label"].num_classes
dataset_size = info.splits["train"].num_examples
dataset_size
Warning: TFDS's split API has evolved since the book was published. The new split API (called S3) is much simpler to use:
test_set_raw, valid_set_raw, train_set_raw = tfds.load(
"tf_flowers",
split=["train[:10%]", "train[10%:25%]", "train[25%:]"],
as_supervised=True)
plt.figure(figsize=(12, 10))
index = 0
for image, label in train_set_raw.take(9):
index += 1
plt.subplot(3, 3, index)
plt.imshow(image)
plt.title("Class: {}".format(class_names[label]))
plt.axis("off")
plt.show()
Basic preprocessing:
def preprocess(image, label):
resized_image = tf.image.resize(image, [224, 224])
final_image = keras.applications.xception.preprocess_input(resized_image)
return final_image, label
Slightly fancier preprocessing (but you could add much more data augmentation):
def central_crop(image):
shape = tf.shape(image)
min_dim = tf.reduce_min([shape[0], shape[1]])
top_crop = (shape[0] - min_dim) // 4
bottom_crop = shape[0] - top_crop
left_crop = (shape[1] - min_dim) // 4
right_crop = shape[1] - left_crop
return image[top_crop:bottom_crop, left_crop:right_crop]
def random_crop(image):
shape = tf.shape(image)
min_dim = tf.reduce_min([shape[0], shape[1]]) * 90 // 100
return tf.image.random_crop(image, [min_dim, min_dim, 3])
def preprocess(image, label, randomize=False):
if randomize:
cropped_image = random_crop(image)
cropped_image = tf.image.random_flip_left_right(cropped_image)
else:
cropped_image = central_crop(image)
resized_image = tf.image.resize(cropped_image, [224, 224])
final_image = keras.applications.xception.preprocess_input(resized_image)
return final_image, label
batch_size = 32
train_set = train_set_raw.shuffle(1000).repeat()
train_set = train_set.map(partial(preprocess, randomize=True)).batch(batch_size).prefetch(1)
valid_set = valid_set_raw.map(preprocess).batch(batch_size).prefetch(1)
test_set = test_set_raw.map(preprocess).batch(batch_size).prefetch(1)
plt.figure(figsize=(12, 12))
for X_batch, y_batch in train_set.take(1):
for index in range(9):
plt.subplot(3, 3, index + 1)
plt.imshow(X_batch[index] / 2 + 0.5)
plt.title("Class: {}".format(class_names[y_batch[index]]))
plt.axis("off")
plt.show()
plt.figure(figsize=(12, 12))
for X_batch, y_batch in test_set.take(1):
for index in range(9):
plt.subplot(3, 3, index + 1)
plt.imshow(X_batch[index] / 2 + 0.5)
plt.title("Class: {}".format(class_names[y_batch[index]]))
plt.axis("off")
plt.show()
base_model = keras.applications.xception.Xception(weights="imagenet",
include_top=False)
avg = keras.layers.GlobalAveragePooling2D()(base_model.output)
output = keras.layers.Dense(n_classes, activation="softmax")(avg)
model = keras.models.Model(inputs=base_model.input, outputs=output)
for index, layer in enumerate(base_model.layers):
print(index, layer.name)
for layer in base_model.layers:
layer.trainable = False
optimizer = keras.optimizers.SGD(learning_rate=0.2, momentum=0.9, decay=0.01)
model.compile(loss="sparse_categorical_crossentropy", optimizer=optimizer,
metrics=["accuracy"])
history = model.fit(train_set,
steps_per_epoch=int(0.75 * dataset_size / batch_size),
validation_data=valid_set,
validation_steps=int(0.15 * dataset_size / batch_size),
epochs=5)
for layer in base_model.layers:
layer.trainable = True
optimizer = keras.optimizers.SGD(learning_rate=0.01, momentum=0.9,
nesterov=True, decay=0.001)
model.compile(loss="sparse_categorical_crossentropy", optimizer=optimizer,
metrics=["accuracy"])
history = model.fit(train_set,
steps_per_epoch=int(0.75 * dataset_size / batch_size),
validation_data=valid_set,
validation_steps=int(0.15 * dataset_size / batch_size),
epochs=40)
base_model = keras.applications.xception.Xception(weights="imagenet",
include_top=False)
avg = keras.layers.GlobalAveragePooling2D()(base_model.output)
class_output = keras.layers.Dense(n_classes, activation="softmax")(avg)
loc_output = keras.layers.Dense(4)(avg)
model = keras.models.Model(inputs=base_model.input,
outputs=[class_output, loc_output])
model.compile(loss=["sparse_categorical_crossentropy", "mse"],
loss_weights=[0.8, 0.2], # depends on what you care most about
optimizer=optimizer, metrics=["accuracy"])
def add_random_bounding_boxes(images, labels):
fake_bboxes = tf.random.uniform([tf.shape(images)[0], 4])
return images, (labels, fake_bboxes)
fake_train_set = train_set.take(5).repeat(2).map(add_random_bounding_boxes)
model.fit(fake_train_set, steps_per_epoch=5, epochs=2)
def maximum_precisions(precisions):
return np.flip(np.maximum.accumulate(np.flip(precisions)))
recalls = np.linspace(0, 1, 11)
precisions = [0.91, 0.94, 0.96, 0.94, 0.95, 0.92, 0.80, 0.60, 0.45, 0.20, 0.10]
max_precisions = maximum_precisions(precisions)
mAP = max_precisions.mean()
plt.plot(recalls, precisions, "ro--", label="Precision")
plt.plot(recalls, max_precisions, "bo-", label="Max Precision")
plt.xlabel("Recall")
plt.ylabel("Precision")
plt.plot([0, 1], [mAP, mAP], "g:", linewidth=3, label="mAP")
plt.grid(True)
plt.axis([0, 1, 0, 1])
plt.legend(loc="lower center", fontsize=14)
plt.show()
Transpose convolutions:
tf.random.set_seed(42)
X = images_resized.numpy()
conv_transpose = keras.layers.Conv2DTranspose(filters=5, kernel_size=3, strides=2, padding="VALID")
output = conv_transpose(X)
output.shape
def normalize(X):
return (X - tf.reduce_min(X)) / (tf.reduce_max(X) - tf.reduce_min(X))
fig = plt.figure(figsize=(12, 8))
gs = mpl.gridspec.GridSpec(nrows=1, ncols=2, width_ratios=[1, 2])
ax1 = fig.add_subplot(gs[0, 0])
ax1.set_title("Input", fontsize=14)
ax1.imshow(X[0]) # plot the 1st image
ax1.axis("off")
ax2 = fig.add_subplot(gs[0, 1])
ax2.set_title("Output", fontsize=14)
ax2.imshow(normalize(output[0, ..., :3]), interpolation="bicubic") # plot the output for the 1st image
ax2.axis("off")
plt.show()
def upscale_images(images, stride, kernel_size):
batch_size, height, width, channels = images.shape
upscaled = np.zeros((batch_size,
(height - 1) * stride + 2 * kernel_size - 1,
(width - 1) * stride + 2 * kernel_size - 1,
channels))
upscaled[:,
kernel_size - 1:(height - 1) * stride + kernel_size:stride,
kernel_size - 1:(width - 1) * stride + kernel_size:stride,
:] = images
return upscaled
upscaled = upscale_images(X, stride=2, kernel_size=3)
weights, biases = conv_transpose.weights
reversed_filters = np.flip(weights.numpy(), axis=[0, 1])
reversed_filters = np.transpose(reversed_filters, [0, 1, 3, 2])
manual_output = tf.nn.conv2d(upscaled, reversed_filters, strides=1, padding="VALID")
def normalize(X):
return (X - tf.reduce_min(X)) / (tf.reduce_max(X) - tf.reduce_min(X))
fig = plt.figure(figsize=(12, 8))
gs = mpl.gridspec.GridSpec(nrows=1, ncols=3, width_ratios=[1, 2, 2])
ax1 = fig.add_subplot(gs[0, 0])
ax1.set_title("Input", fontsize=14)
ax1.imshow(X[0]) # plot the 1st image
ax1.axis("off")
ax2 = fig.add_subplot(gs[0, 1])
ax2.set_title("Upscaled", fontsize=14)
ax2.imshow(upscaled[0], interpolation="bicubic")
ax2.axis("off")
ax3 = fig.add_subplot(gs[0, 2])
ax3.set_title("Output", fontsize=14)
ax3.imshow(normalize(manual_output[0, ..., :3]), interpolation="bicubic") # plot the output for the 1st image
ax3.axis("off")
plt.show()
np.allclose(output, manual_output.numpy(), atol=1e-7)
See appendix A.
Exercise: Build your own CNN from scratch and try to achieve the highest possible accuracy on MNIST.
The following model uses 2 convolutional layers, followed by 1 pooling layer, then dropout 25%, then a dense layer, another dropout layer but with 50% dropout, and finally the output layer. It reaches about 99.2% accuracy on the test set. This places this model roughly in the top 20% in the MNIST Kaggle competition (if we ignore the models with an accuracy greater than 99.79% which were most likely trained on the test set, as explained by Chris Deotte in this post). Can you do better? To reach 99.5 to 99.7% accuracy on the test set, you need to add image augmentation, batch norm, use a learning schedule such as 1-cycle, and possibly create an ensemble.
(X_train_full, y_train_full), (X_test, y_test) = keras.datasets.mnist.load_data()
X_train_full = X_train_full / 255.
X_test = X_test / 255.
X_train, X_valid = X_train_full[:-5000], X_train_full[-5000:]
y_train, y_valid = y_train_full[:-5000], y_train_full[-5000:]
X_train = X_train[..., np.newaxis]
X_valid = X_valid[..., np.newaxis]
X_test = X_test[..., np.newaxis]
keras.backend.clear_session()
tf.random.set_seed(42)
np.random.seed(42)
model = keras.models.Sequential([
keras.layers.Conv2D(32, kernel_size=3, padding="same", activation="relu"),
keras.layers.Conv2D(64, kernel_size=3, padding="same", activation="relu"),
keras.layers.MaxPool2D(),
keras.layers.Flatten(),
keras.layers.Dropout(0.25),
keras.layers.Dense(128, activation="relu"),
keras.layers.Dropout(0.5),
keras.layers.Dense(10, activation="softmax")
])
model.compile(loss="sparse_categorical_crossentropy", optimizer="nadam",
metrics=["accuracy"])
model.fit(X_train, y_train, epochs=10, validation_data=(X_valid, y_valid))
model.evaluate(X_test, y_test)
Exercise: Use transfer learning for large image classification, going through these steps:
See the Flowers example above.
Exercise: Go through TensorFlow's Style Transfer tutorial. It is a fun way to generate art using Deep Learning.
Simply open the Colab and follow its instructions.